Hundreds of homes are at risk of being washed away by fast-flowing floodwaters in the Australian state of Queensland.

Mass evacuations have been carried out in the city of Bundaberg, north of Brisbane, where waters in the Burnett River continued to rise above the record level of nine metres.

Up to 2,000 properties have been flooded and the state's premier, Campbell Newman, told reporters the emergency was widespread.

"These are record floods and we are in unchartered territory," he said.

"The water is flowing extremely fast. Some estimates have put it at 40 knots, which makes the rescue of people extremely hazardous or downright impossible, particularly with debris in the river system.

"We are also very concerned that the velocity of the river and the rise in water levels means that literally, houses, particularly in north Bundaberg, could be swept away. This is a very real prospect."

Wild weather conditions generated by the former cyclone Oswald have pounded Queensland's southeast over the past several days, leaving at least three dead and thousands of homes either damaged or destroyed.

By Tuesday, around 3,500 homes and 1,500 business have been told to expect flooding as high tides are swollen by the high levels of rainfall in the region.

The city of Ipswich, west of Brisbane, which also experienced widespread devastation in January 2011, is also due to flood again as the Bremer River peaked at 15 metres.

On Monday, the Brisbane River had already broken its banks in parts of the city centre, flooding parks and bike paths.

The expected peak of 2.6 metres is almost two metres lower than in 2011, and the authorities have been keen to stress the crisis in the city of two million people is not as severe.

But after dozens of suburbs were inundated only two years ago, emotions in Brisbane and Ipswich are still raw.

Earlier this month a law firm announced it was putting together a class action on behalf of flood victims who accuse authorities of mismanaging the release of water from Wivenhoe Dam.

The dam was built after the devastating 1974 flooding of Brisbane, which left vast areas of the city under water.

Two years ago authorities had no choice but to release an extraordinary amount of water from the dam to save the structure from giving way.

But Mr Newman, who was mayor of Brisbane in January 2011, said the circumstances of this year's flooding event are different.

"Running a dam is quite a complex operation. The best way I can explain to people, the operation of a dam like a shock-absorber in your car. It's designed to take the impacts. Take the bumps out of the road," he said.

"What the people running the dam are doing is everything they can to take the shock out of the system and to ensure we have the lowest possible water levels in the Brisbane River.

"But there is flooding in the Lockyer (Valley), there's flooding in the Bremer River, and those watercourses go in to the Brisbane River downstream from Wivenhoe Dam. They cannot be controlled.